The wall stretches for nearly 40-miles long and is re-enforced with remote cameras and regular patrols.

The tightening of pressure on Ukraine has been condemned by several European leaders who have called for a definitive end to the conflict which came about after Russia annexed Crimea from Ukraine in 2014, violating international laws.

"The human rights situation in Crimea, illegally annexed by Russia, Russia's use of military force in the Kerch Strait, as well as the excessive inspections carried out in the Sea of ​​Azov, are also ... 'a deep concern," the joint statement said. "We call for all vessels in the Kerch Strait to have a safe, free and unhindered passage and for the immediate and unconditional release of Ukrainian seamen. They too must be able to spend the holidays with their families."

There have been several cease-fires since Russia annexed Crimea including one that was due to begin Saturday, but Ukraine military violated the ceasefire, shelling the militia's positions in the self-proclaimed Lugansk People's Republic in eastern Ukraine, the LPR mission to the Joint Center for Control and Coordination said in a statement Saturday.